<!DOCTYPE html>
<html>
<head>
	<title>声明一个变量</title>
</head>
<body>
	<div id="div">this is div</div>
</body>
<script type="text/javascript">
	var variable;
	variable = 'nihao';
	document.write(variable);
	variable = "hello";
	document.write(variable);
	document.getElementById("div").innerHTML = "change div";
</script>
</html>